The invention concerns a structural assembly for a motor vehicle dashboard incorporating an air duct.
In a customary manner, dashboards are known which comprise a metal cross-member relative to which flexible air ducts are fixed.
On the other hand, U.S. Pat. No. 5,358,300 describes a dashboard structural assembly comprising a structural member consisting of a plurality of ribbed plates fixed to one another, defining air ducts between them and having a mechanical strength such that said assembly is devoid of a metal cross-member.
Moreover, FR-A-2 808 480 describes an air diffuser duct comprising a first member having sufficient rigidity to have a shape of its own and a second member having no rigidity of its own. These two members define between them an air circulation channel. In addition, a groove is provided in the first member for receiving electric cables and the second member covers over the groove, in order to maintain the electric cables therein. Said duct is fixed on a tubular cross-member belonging to the structure of the vehicle.
The object of the invention is to propose a structural assembly which is easy to produce, robust, of reduced weight and offering optimum protection for the occupants of the vehicle in which said assembly will be mounted.
In order so to do, according to the invention, said assembly comprises:
a metal cross-member extending in a direction of elongation, and
a structural member made of plastics material moulded on the metal cross-member and having a passage forming an air duct, said air duct being beside the metal cross-member relative to which it extends substantially parallel.
The metal cross-member takes up the essential part of the mechanical stresses, thereby guaranteeing great robustness and a relatively simple design. In addition, since the structural member not only provides the ventilation function, but in addition withstands part of the mechanical stresses, the metal cross-member may be of smaller section.
The over-moulding of the cross-member ensures a robust connection between the cross-member and the structural member, good cohesion and a good compactness of the assembly, as well as an improved simplicity of production.
Moreover, the relative arrangement of the structural member and of the cross-member ensures not only satisfactory distribution of the efforts between these two members, but above all, by improving the compactness, it increases the length of deformation of the vehicle before intrusion inside the passenger compartment.
In fact, in general, the vehicles comprise a connecting plate extending between the dashboard structural assembly and a secondary cross-member extending at the base of the windscreen and termed lower aperture cross-member. In the event of a shock, there is a risk of the connecting plate pushing the dashboard structural assembly inside the passenger compartment of the vehicle. By increasing the compactness of said dashboard structural member, the distance separating said lower aperture cross-member and the dashboard structural member is increased, in other words, the risk of intrusion inside the passenger compartment of the vehicle is reduced.
According to an advantageous feature according to the invention, the air duct has:
a main portion, substantially rectilinear, extending substantially in said direction of elongation in a substantially horizontal plane passing through the metal cross-member,
at least one secondary portion, substantially curved, prolonging the main portion, departing gradually from said substantially horizontal plane and passing over the metal cross-member.
Thus, the metal cross-member is not mechanically weakened at the site of the overlap with the duct and the assembly frees a space in the dashboard above the main portion of the transverse structure for accommodating different accessories therein (air bag box, instrument panel, storage, etc.).
In a complementary manner, according to the invention, the cross-member has a section substantially having an open U-shape defining a hollow and the transverse structure comprises ribs extending into said hollow of the cross-member.
The U-shaped section makes it possible to obtain a satisfactory ratio between the mechanical strength and the weight. Moreover, it allows the ribs to be disposed easily within the hollow in order to prevent the section of the cross-member from distorting, without noticeably increasing the weight.
In a complementary manner, an advantageous feature of the invention making it possible to produce the assembly easily while preventing the air circulating in the duct from penetrating between the ribs, generating noise and losses of load, consists in that:
the structural member comprises a body incorporating the cross-member and a covering cap, between which the air duct extends,
the air duct passes over the cross-member in an intersection zone,
the assembly further comprises in the intersection zone a layer of ventilation foam extending over the ribs.
Thus, the body and the covering cap of the structural member may be easily obtained by moulding and the intersection zone does not have the aforementioned drawbacks.
The invention further proposes that the duct comprises a protuberance intended for fixing a vehicle steering column to the structural member and that the protuberance is filled at least partially with ventilation foam.
Thus, the shape of the structural member is adapted to support the steering column without complicating its production by moulding or disturbing the flow of air in the duct.